The present invention relates to a measuring assembly consisting of an assemblage of measuring elements lowered in a well to perform what is referred to as logging operations in the profession. The assembly or sonde is generally several ten meters long. Certain measuring elements can require a particular orientation with respect to the axis of the well in order to perform measurements in a preferred direction.
In this case, the well-known technique for orienting certain measuring elements of a logging sonde consists in rotating about its axis the entire measuring assembly by applying a rotation to the operating rods at the end of which the sonde is fastened.
This operation entails several drawbacks:
Controlling the orientation of the measuring elements is difficult in wells where friction on the sonde and the rods is high. This is the case with deflected wells and particularly horizontal wells where the friction is such that the torsional deformation of the rods and of the sonde prevents precise control of the angular position. PA1 Furthermore, under such conditions, the imperfect control of the effect of a surface rotation on the sonde can lead to a twistoff at the level of the sonde whose inertia is generally lower than that of the operating rods. PA1 In horizontal wells notably, the weight of the sonde can be such that the rotation from the surface may be ineffective for driving the entire sonde into rotation.